1844'.] of Bodies generally existing as Gases. 101 



down in a vertical direction. One of the glass condensing 

 siphon tubes, already described, fig. 1, was screwed on to the 

 lower end of the sliding tube, and the upper end of the latter 

 was connected with a communicating tube in two lengths, 

 reaching from it to the condensing pumps ; this tube was small, 

 of brass, and 9J feet in length ; it passed 6 inches horizontally 

 from the condensing pumps, then rose vertically for 2 feet, after- 

 wards proceeded horizontally for 7 feet, and finally turned down 

 and was immediately connected with the sliding tube. By this 

 means the latter could be raised and lowered vertically, without 

 any strain upon the connexions, and the condensing tube low- 

 ered into the cold bath in vacuo, or raised to have its contents 

 examined at pleasure. The capacity of the connecting tubes 

 beyond the last condensing pump was only 2 cubic inches. 



When experimenting with any particular gas, the apparatus 

 was put together fast and tight, except the solid terminal 

 screw-plug at the short end of the condensing tube, which, 

 being the very extremity of the apparatus, was left a little 

 loose. Then, by the condensing pumps, abundance of gas was 

 passed through the apparatus to sweep out every portion of 

 air, after which the terminal plug was screwed up, the cold bath 

 arranged, and the combined effects of cold and pressure 

 brought to unite upon the gas. 



There are many gases which condense at less than the press- 

 ure of one atmosphere when submitted to the cold of a car- 

 bonic acid bath in air (which latter can upon occasions be 

 brought considerably below 106 Fahr.). These it was easy, 

 therefore, to reduce, by sending them through small conduct- 

 ing tubes into tubular receivers placed in the cold bath. When 

 the receivers had previously been softened in a spirit-lamp 

 flame, and narrow necks formed on them, it was not difficult, 

 by a little further management, hermetically to seal up these 

 substances in their condensed state. In this manner chlorine, 

 cyanogen, ammonia, sulphuretted hydrogen, arseniuretted hy- 

 drogen, hydriodic acid, hydrobromic acid, and even carbonic 

 acid, were obtained, sealed up in tubes in the liquid state ; and 

 euchlorine was also secured in a tube receiver with a cap and 

 screw-plug. By using a carbonic acid bath, first cooled in 

 vacuo, there is no doubt other condensed gases could be se- 

 cured in the same way. 



